1. Field of the Invention
The present invention relates generally to the field of communication systems. More specifically, the present invention relates to recognizing audio and video streams over Point-to-Point Protocol (xe2x80x9cPPPxe2x80x9d) links.
2. Description of the Related Art
With recent developments in the area of multimedia data processing in the Internet and the World Wide Web (xe2x80x9cWWWxe2x80x9d) such as, speech, sound, and image processing, new techniques for managing and transferring multimedia data over communications networks are needed. In other words, a method to transfer multimedia packets over the communication networks with minimal delay is required to meet real time multimedia requirements.
In communication networks utilizing Internet protocol (xe2x80x9cIPxe2x80x9d) (See reference: Information Science Institute, University of Southern California, xe2x80x9cInternet Protocol DARPA Internet Program Protocol Specificationxe2x80x9d, September 1981), real time multimedia data, such as audio and video (xe2x80x9cAVxe2x80x9d) data, is typically transmitted using User Datagram Protocol (xe2x80x9cUDPxe2x80x9d). (See reference: J. Postel, ISI, xe2x80x9cUser Datagram Protocolxe2x80x9d, August 1980). UDP is referred to as an unreliable protocol because UDP normally makes no effort to re-transmit lost packets or to reorder the out of sequence packets during transmission.
High network utilization is one situation that may cause AV packets to reach their destination out of order, or with time delay, or occasionally some packets may fail to reach their destination. A highly utilized communication network may cause multimedia packets to wait for accessing PPP links. Consequently, waited packets often reach their destinations at a later time and sometimes, the arrival sequence of waited packets may be out of order.
When the amount of AV packet loss or out of order is not too severe, AV playback may be audible and viewable with minimum distortion. However, when the amount of AV packet loss or out of order is too severe, the result may be inaudible or confusing.
By contrast, Transmission Control Protocol (TCP), which also runs over IP, is a reliable protocol in which data packets are guaranteed to eventually reach their destinations. The packets which are transmitted using TCP, are numbered in sequence when first transmitted so that upon a retry or retransmission, the packets can be ordered correctly. However, the disadvantage of TCP is slowness, which is caused by the process of numbering packets in sequence and by multiple retransmission necessary to improve reliability. TCP is normally utilized for transferring text binary files and control messages, which do not ordinarily need real time transfer, but it is important that transmitted packets eventually be received intact and in order at their intended destinations.
When transporting streams of multimedia packets over the network, it is important for multimedia packets to be transmitted without delay since real time multimedia packets have tight latency and jitter requirements. However, these tight latency and jitter requirements are often violated when multimedia packets are transmitted across PPP links due to the low bandwidth typically available over such links. It is common for such low bandwidth PPP links to simultaneously be used for both multimedia, which may be carried by UDP, and data streams, which maybe carried by TCP. This scenario is often known as simultaneous AV and data xe2x80x9cSAVDxe2x80x9d. SAVD often takes all available bandwidth by TCP streams resulting in delivery of audio/video streams with unacceptable levels of loss and jitter.
One way to minimize loss of multimedia packets and to enhance quality of services is to transport AV packets in a lightly loaded link (e.g., the user is not simultaneously browsing the WWW, downloading files by FTP, etc.). The disadvantage of this method is that if a PPP link is initially lightly loaded but subsequently loaded while transferring the multimedia packets, it will cause significant degradation in quality of service, especially for multimedia data.
Another way to improve the quality of service for multimedia streams is using announcement protocols. This option involves using a PPP link in conjunction with Compressed Real Time Protocols (xe2x80x9cCRTPxe2x80x9d) (see reference: S. Casner, V. Jacobson, xe2x80x9cCompressing IP/UDP/RTP Headers for Low-Speed Serial Linksxe2x80x9d, Internet-Draft (draft-ietf-avt-crtp-04.txt), March 1997.) and Multi-Channel Multi-Links PPP (xe2x80x9cMCMLxe2x80x9d) (see reference: C. Bormann, xe2x80x9cThe Multi-Class Extension to Multi-Link PPPxe2x80x9d, Internet-Draft (draft-ietf-issll-isslow-mcml-03.txt), May 1997.) or Real Time Framing (xe2x80x9cRTFxe2x80x9d) (see reference: C. Bormann, xe2x80x9cPPP in a real-time oriented HDLC-Like framingxe2x80x9d, Internet-Draft (draft-ietf-issll-isslow-rtf-02.txt), September 1998.) along with an announcement protocol, such as RSVP. See reference: R. Braden, Ed., et. al.,xe2x80x9cResource Reservation Protocol (RSVP)xe2x80x94Version 1 Functional Specificationxe2x80x9d, RFC 2205, September 1997. This method relies on announcement protocols to determine which stream requires more than best-effort service and what level and type of services to provide for such streams. Best-effort service is referred to a default quality of service that a conventional communication network offers. However, RSVP and other announcement protocols have not yet been widely deployed across intranet and Internet environments. Furthermore, announcement protocols require changes to applications to indicate the need for special treatment of the streams they transmit/receive.
Accordingly, it is desirable to have a mechanism that can recognize AV packets and is capable of enhancing the quality of service for AV packets using MCML or RTF over PPP links in the absence of announcement protocols.
A method and apparatus for enhancing quality of network service for multimedia streams over Point-to-Point Protocol (xe2x80x9cPPPxe2x80x9d) links in the absence of announcement protocols are disclosed.
In one embodiment, a method for improving data communications based on the quality of service (xe2x80x9cQOSxe2x80x9d) for multimedia streams over PPP links includes identifying audio and video packets from data streams independent of the presence of announcement protocols. The method further includes prioritizing packets to be transferred over the links according to information that each packet carries.
In another embodiment, an apparatus is designed to enhance QOS for multimedia frames over PPP links to recognize multimedia packets from incoming data frames in the absence of an announcement protocol. The apparatus further prioritizes the packets to be transmitted over the links in response to the information that each packet carries and subsequently transfers the priority classes along with associated packets over the links.
Additional features and benefits of the present invention will become apparent from the detailed description, figures and claims set forth below.